Electromagnet



Jan. 10, 1928.

H. W. BROWN ELECTROMAGNET Filed May 15, 1923 LEMQQD GAP.

Inventor Hero/d W UFO W17,

H/s Attorney.

GAP:

Patented Jan, Ml), 19280 UNHTEE STATES M03410 W. BROWN, F SCHENECTADY, NEW YORK, ASSIGNOR T0 GENERAL ELECEREG GOMPANY, A CORPORATION OF NEW YGBK. i

ELECTROMAGNET.

Application filed may 15, 1923. Serial No. 639,194.

My invention relates to improvements in upper end hollow, The plunger 11 forms electromagnets and more particularly to with the pole piece 3 an air gap which 55 electromagnets for electro-responsive protecvaries according to the position of the tive devices or relays operative in response plunger, which is adjustably mounted on the 5 to predetermined abnormal circuit condirod and positively secured thereon in a tions and has for an object to provide an given position by any suitable means such improved electromagnetic structure such as a lock nut 13. The rod 10 may be arthat relays embodying my invention may ranged to control by its movement suitable have a broad range of operating values contact controlling means as is well known 10 My invention will be better understood to the art.

from the following description taken in con- With this construction, it is obvious that nection with the accompanying drawing and the tubular member 7 and the plunger 11 5-3 its scope will be pointed out in the appended form parallel paths for the flux of the elecclaims, tromagnet from the tubular member and 15 Fig. 1 illustrates in section an electroarmature across their respective air gaps to magnet embodying my invention and Figs. the pole piece 3. Consequently the distribu- 2 and 3 are typical characteristic curves iltion of the total flux in these parallel paths in lustrating the relation between current and depends upon the relative values of the air gap and between flux and gap in electrogaps, that is to say the position of the 2 magnets embodying my invention. plunger 11 relatively to the tubular mem- In Fig. 1 my invention is illustrated as ber 7. The position of the plunger 11 may applied to an electromagnet of the solenoid be varied by adjusting the plunger relatively and plunger type comprising a magnetic to the rod 10 thereby varying the air gap structure such as a housing or frame 1 and between the pole piece 3 and the plunger 11 25 a cover or top portion 2 provided with a or the plunger may be moved through the pole piece or polar extension 3 which may tubular member 7 by any suitable actuating be fixed. In the magnetic structure, there means such as a pinion 14 arranged to enis mounted on a liner or spacer at of gage a rack 15 on the rod 10, the plunger non-magnetic material an insulating spool being free to move independently of the 30 5 on which is wound an energizing rack 15 so that, when the current attains a winding such as a solenoid 6- Mounted pick up value corresponding to the gap bein the frame 1 is a magnetic shield tween the plunger 11 and the pole piece 3,

such as a tubular magnetic member or holthe plunger will be moved to attractive polow pole piece 7 which is spaced from the sion. Any suitable actuating means may be pole piece 3 to form a predetermined air gap employed operative preferably automatiand is preferably adjustably positioned in cally in response to the conditions on an the frame 1 so that this air gap may be electric circuit by a motor mechanism such,

varied to provide diiferent operating charfor example, as that disclosed in United acteristics. The tubular member 7 may be States Letters Patent 1,240,723 issued to 4 positively secured in a given position by any E. H. Jacobs, September 18, 1917 and assuitable means such as a lock nut 8 and is signed to the same assignee as this invenpreferably provided with a liner 9 of nontion, or the mechanism, disclosed in United magnetic material. Mounted on a movable States Letters Patent 1,481,938 issued to member such as a rod 10 for movement O. G. Traver January 29, 1924, and assigned 45 through the tubular member 7 is an armato the same assignee as this invention, may ture or plunger 11 of magnetic material. be employed but as such mechanism forms The plunger 11 is preferably tubular and no part of the present invention, it is not may be provided with heads 12 of nonillustrated in this application While elec magnetic material. In case a greater pull tromagnets embodying my invention are 50 is desired with the shielding effect of the particularlv well adapted to electrorespontubular member 7 less pronounced, the upsive protective devices in which a wide range per head 12 may be of magnetic material or of operating values is desired and to electhe plunger 11 may be made solid with the troresponsive devices of the type disclosed in the afoi'esaid patents, it is to be understood thatmy invention is not limited in its application to such devices.

. In the following discussion of the operation of electromagnets embodying my invention, it will be assumed that the load to be overcome by the electromagnet in picking up and moving the plunger 11 to attracted position is substantially constant, this being the case generally.

With the plunger .11 invthe position shown in Fig. 1, more or less of the total flux will go through the tubular member 7, the amount depending upon the depth or submergence of the plunger 11 in the tubular member 7 that is to say the shielding effect of the member 7, while the balance of the flux, excluding leakage flux, will go through the plunger 11. The characteristic of the total flux necessary before the plunger 11 will be picked up and moved to attracted position for a given air gapbetween. the

- neprwsentedby the 1 plunger 11 and the pole piece 3-when the hunger is below the top of the tubular memr 7 is represented by the full line portion 17-18 of the curve 16-17-18 of Fig. 3. The curve 161718 represents the total flux in the electromagnet as plotted against .the air gap between the plunger 11 and the pole piece 3, the solid line portion 17-18 to the right of the vertical broken line 19 representing conditions when the plun er 11 is below the top of the tubular mem er 7. It will be observed from the portion I'l -18 of-Fi 3, thatthe total flux required before the p unger 11 will be picked up increases very rapidly with an increase in the air gap ,between the plunger and the pole piece 3, that is to say with the plunger lower in the tubular vmember 7. As the plunger 11, however, moves up through the tubular member 7, thereby decreasing the air gap between itself and the pole piece 3, the total flux necessary to ick up the plunger rapid- 1y decreases and comes substantially constant as indicated by the full line portion 1617 of the curve 16.1'Z18, This occurs when the top of the plunger 11 is about even with the top of the tubular member 7, that is, when the end of the plunger 11 adjacent the pole piece 3 begins to emer e from the magnetic shield 7. Without t e tubular memher Y, the flux characteristic would be as indicated by the curve' 16-1720, which is substantially a straight line,

The characteristic of the current necessary to pick the plunger 11 and move it to attracted position for a given air gap be tween the plunger and the pole piece 3-is line portion 17-18 of the curve 16'17 '18 in Fig. 2, which represents the pick up or operating current as plotted against the air gap between the plunger and the pole piece 3. it will, be

ehserved from the, portion 17-18 of'the eeaaea curve 16'- 17'18 of Fig. 2 that the operat- V to pickup the plunger rapidly decreases at a rate which is greater than the rate of decrease'of the air gap, that is to say a small change in the air ap produces a relatively large change in t e pick up current required, the rate of change of current being greater the farther down the plunger is in the tubular member 7 As the plunger 11 moves up through the tubular member 7 the pick up current required rapidly decreases both in value and rate of change until the rate of change becomes substantially constant as indicated by the full line portion 16'17 of the curve to the left of the vertical broken line 19. This occurs when the top of the plunger is about even with the top of the tubular member 7 Without the shielding effect of the tubular member 7, the current characteristic would be substantially as indicated by the curve 16'17'-20' which is substantially a straight line and the rate of change of pick up current with respect to air gap would be substantially con-- stant so that an excessively long air gap, from a practical standpoint, would be required to obtain-such a wide range of operating values as is provided by electromagnets embodying m invention.

What I claim as new and desire to secure by Letters Patent of the United States, is

1. An electromagnet. comprising an energizing winding, a magnetic structure associated therewith and comprising a pole piece, a magnetic shield mounted in said structure and spaced from said pole piece to form an air gap and an armature extending into said shield and mounted for movement therethrough relatively to said pole piece to form therewith a variable air gap greater than the ga between said shield and said pole piece t roughout a part of the movement of the armature whereby parallel paths are provided for the flux from said armature and said shield across said air gaps to said pole piece such thatthe distribution of the flux is dependent on the relative values of said air gaps. L

2. An electromagnet comprising an energizin winding, a magnetic structure associ-ate therewith and comprising a fixed pole 7 piece, a ma etic shield adjustably positioned in sai magnetic structure and spaced from said pole piece to form an air gasp, and an armature mounted for movement through said shield toward and from said pole piece to provide a variable air gap be tween the armatnre and the pole piece, said ular member forming armature and said shield forming parallel paths for flux therefrom to said pole piece whereby the distribution of the flux in said paths is dependent upon the position of the armature in said shield.

3. An electromagnet comprising a solenoid, a magnetic structure associated therewith and comprising a pole piece, a tubular magnetic member adjustably mounted on said magnetic structure, said tubular member being spaced from said pole piece to form an air gap, a member movable through said tubular member, and an armature mounted on said movable member and extending into said tubular member to provide upon actuation of the movable member a change in the relative values of the air gaps between the pole piece and the end of the armature adjacent thereto and between the pole piece and the tubular member, said armature and said tubparallel paths for flux therefrom to said pole piece whereby the distribution of the flux in said paths is dependent upon the position of said armature relatively to said tubular member.

4. An electromagnet comprising a solenoid, a magnetic structure associated therewith and comprising a pole piece, a tubuular magnetic member mounted on said magnetic structure and extending into said solenoid, said'ttubularmember being spaced from said pole piece to form a predetermined air gap, an armature extending into said tubular member and mounted for movement therethrough relatively to said pole piece to form therewith a variable air gap greater than the gap between said tubular member and said pole piece throughout a predetermined range of movement of the armature, whereby parallel paths are provided for the flux from said armature and said tubular member across said air gaps to said pole piece such that the distribution ofthe flux is dependent upon the relative values of said air a s. g An electromagnet comprising a solenoid, a magnetic structure associated therewith and comprising a pole piece, a tubular magnetic member adjustably positioned in said magnetic structure and extending into said solenoid, said tubular member being spaced from said pole piece to form a, predetermined air gap for any given position of adjustment, a movable member, an armature adjustably positioned on said movable member and mounted for movement through said tubular member, said armature extending into said tubular member and forming with said pole piece a variable air gap greater than the gap between said tubular member and said pole piece throughout a predetermined vrange of movement of the armature, whereby parallel paths are provided for the flux from said armature and said tubular member across said air gap to said pole piece such that the distribution of the flux across said air gaps is dependent upon the position of said armature relatively to said tubular member.

6. An electromagnet comprising an energizing winding, a magnetic structure associated therewith and comprising a pole piece, a magnetic shield mounted in said structure and spaced from said pole piece to form an air gap, and an armature having one end normally submerged in said shield arranged for movement therethrough and to emerge therefrom to" form said end and said pole piece.

7. An electromagnet comprising an energizing winding, a magnetic structure associated therewith and comprising a pole piece, a magnetic shield mounted in said structure and spaced from said pole piece to form an air gap, and an armature having the end thereof adjacent said pole piece normally submerged in said shield and arranged for movement therethrough and to emerge therefrom to form a variable air gap with said pole piece.

8. An electromagnet comprising an energizing winding, a magnetic structure associated therewith and comprising a pole piece, a magnetic shield mounted in said structure and spaced from said pole piece to form an air gap, and an armature having one end normally submerged in said shield and arranged for movement therethrough and to emerge therefrom to form adecreasing air gap with said pole piece.

In witness whereof, my hand this 10th day I have hereunto set of May, 1923.

HAROLD W. BROWN.

a variable air gap between 

